Update the session object with the error msg from ApexSessionInfo

Now that apexd returns an error message with details about why APEX
activation has failed, we can append it to session object's error
message.

Bug: 178192690
Test: atest
StagedInstallInternalTest#testApexActivationFailureIsCapturedInSession

Change-Id: Id2d1df7f86ca85b044cfa15990eae548a176882b
5 files changed